Respiratory treatment apparatuses involves the delivery of a pressurized breathable gas, such as air, oxygen enriched air or oxygen, to a patient's airways using a conduit and patient interface device. Gas pressures employed typically range from 4 cm H20 to 30 cm H20, at flow rates of up to 180 L/min (measured at the mask), depending on patient requirements. For CPAP the pressurized gas acts as a pneumatic splint for the patient's airway in a CPAP device, preventing airway collapse, especially during the inspiratory phase of respiration. For ventilation the apparatus is designed to move breathable gas into and out of the patients' lungs.
The advantages of incorporating humidification of the air supply to a patient are known, and respiratory apparatuses are known which incorporate humidifying devices. Such respiratory apparatuses commonly have the ability to alter the humidity of the breathable gas in order to reduce drying of the patient's airway and consequent patient discomfort and associated complications. The use of a humidifier unit placed between the flow generator and the patient mask produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. In addition in cooler climates, warm air applied generally to the face area in and about the mask is more comfortable than cold air.
Many humidifier types are available, including humidifier that are either integrated with or configured to be coupled to the relevant respiratory apparatus. If integrated within the relevant respiratory apparatus the humidifier is generally formed in a separate portion of the apparatus to the blower to prevent water entering the blower. While passive humidifiers can provide some relief, generally a heated humidifier is required to provide sufficient humidity and temperature to the air so that the patient will be comfortable. Humidifiers typically comprise a water tub having a capacity of several hundred milliliters, a heating element for heating the water in the tub, a control to enable the level of humidification to be varied, a gas inlet to receive gas from the flow generator, and a gas outlet adapted to be connected to a patient conduit that delivers the humidified gas to the patient's mask.
Typically, the heating element is incorporated in a heater plate which sits under, and is in thermal contact with, the water tub.
Respiratory apparatuses typically include a blower integrated within the apparatus to provide a supply of respiratory gas. The blower comprises an integrated motor having a stationary component and rotating component (or rotor) that are adapted to drive an impeller. The rotating component includes a rotor or shaft coupled to a magnet and the stationary component includes a stator comprising a plurality of wound coils. The stator provides an electromagnetic drive to rotate the magnet and coupled rotor. The impeller is commonly coupled to the shaft or rotor such that it is induced to rotate with the rotor or shaft. The stationary component and rotating components are located together as a motor unit within the blower. Typically the motor has a cylindrical construction, such that the stator with wound coils is aligned vertically to surround the rotor and magnet. Thus, when the motor is energized the wound coils create a magnetic field that causes the magnet to rotate. As the magnet is coupled to the rotor and the rotor is coupled to the impeller, the rotor and impeller are also caused to rotate with the magnet.
U.S. Pat. No. 6,302,105 describes having an impeller located within a separate housing to the motor. However, the motor still comprises a stationary component (wound coils) and rotating component (rotor and magnet). The impeller is not directly coupled to the rotating portion of the motor but is driven to rotate by the addition of extra magnets on the impeller that induce the impeller to rotate in synchrony with the rotating portion of the motor. The separation of the impeller from the motor is said to provide a disposable air path.
Respiratory apparatuses have also been developed to reduce the dangers of biological contamination, such as when used in hospitals for multiple patients. A bacteriological filter may be included to prevent biological material being forced back into the apparatus. In other systems, the respiratory apparatus may be configured to be cleanable or autoclavable.